Feasibility of bio-filter in treating low strength nitrogen wastewater under adverse temperatures

As a promising nitrogen removal technology, anammox still faces the bottlenecks of low temperatures, low substrates, and large wastewater flow in mainstream. This study investigated the feasibility of anammox bio-filter (A-BF) as advanced nitrogen removal unit for sewage treatment in low temperature climates. Results showed when treating 7 mg-NH₄⁺-N·L⁻¹ and 10 mg-NO₂^--N·L⁻¹ wastewater, A-BF achieved 71.8 ± 5.6 % and 60.10 ± 10.31 % of total nitrogen removal efficiency (TNRE) under nitrogen loading rate (NLR) of 1.20 ± 0.30 kg-N m⁻³ d⁻¹, within 0.3 h at 25 and 7.5 °C, respectively, based on ＜8 mg L⁻¹ effluent. Further analysis showed that A-BF performance was recovered with TNRE of 71.8 ± 5.6 % when back to 25 °C after collapsing with TNRE of 24.30 ± 15.73 % at 5 °C. Dominant Candidatus Brocadia in anammox bacteria (AnAOB) (3.59–6.24 %) contributed to higher 0.22 and 0.46 g-N·g-VSS⁻¹·d⁻¹ biomass activity at 25 °C. This study provided possible and low-carbon strategy for advanced nitrogen removal.